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Mikhail Geyfman, Jeffrey Suhalim, Tejas Shah, Cintia De Paiva, Stephen Pflugfelder, Eric Potma, James Jester; Effect of Evaporative Stress on Meibomian Gland Proliferative Status and Lipid-Protein Composition. Invest. Ophthalmol. Vis. Sci. 2013;54(15):922.
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Evaporative environmental stress incorporating exposure to high air flow under low humidity conditions combined with scopolamine-induced lacrimal gland inhibition is a model system that is widely used to assess ocular surface changes related to evaporative dry eye. While studies have shown marked inflammatory and immune effects on the ocular surface, its effect on meibomian gland function remains largely unknown. We sought to evaluate the effects of evaporative stress on meibocyte proliferation and lipid quality.
To induce environmental stress, ten mice were treated with scopolamine and placed in a blower hood under reduce environmental humidity. Five and ten days after treatment, eye lids from the treated (5 mice each) and untreated control mice (5 mice) were harvested and embedded in OCT. Cryosections were prepared and stained with antibodies to Ki67 (marker of cycling cells). Percentage of positive basal acinar cells was determined. Eyelid sections were also imaged using coherent Raman Scattering (CRS) microscopy to characterize the lipid compositional changes in the gland. Specifically, the protein-to-lipid ratio was obtained by tuning the laser beams to probe the vibrational signatures of protein and lipid using the methyl and amide-I vibration for protein and the symmetric stretch and bending modes of methylene to probe lipid. Statistical significance of all data was determined using all pairwise multiple comparison ANOVA (Holm-Sidak method).
Evaporative stress caused a marked 3 fold increase in basal acinar cell proliferation from 18.3 ± 11.1% in untreated mice to 64.4 ± 19.9% and 66.6 ± 13.4% after 5 and 10 days exposure, respectively (P < 0.001). In addition, evaluation of the lipid compartment of the meibomian gland by CRS showed wider variation in the protein-to-lipid ratio throughout the gland suggesting alterations in meibocyte differentiation and lipid synthesis
This data is consistent with a model that evaporative stress may have a direct effect on Meibomian gland function leading to a significant increase in both basal acinar cell proliferation and possibly altered meibocyte differentiation and lipid production. A provocative hypothesis that remains to be tested is that prolonged evaporative stress may causes stem cell exhaustion, and eventual meibomian gland atrophy leading to evaporative dry eye disease.
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